1. Field of the Invention
This invention relates to a drive apparatus for one or more supplemental apparatuses driven by an internal combustion engine.
Supplemental apparatuses used in conjunction with an automotive vehicle engine are generally driven by power produced by the engine. Consequently, in order to realize maximum performance and use available space efficiently, both the structure linking the engine and the supplemental apparatuses and the layout of the engine and the supplemental apparatuses are very important.
Typically, in an engine and supplemental apparatus combination, a compact supplemental apparatus having a low drive load requirement, such as an oil pump for a lubrication and/or a water pump, is disposed near a front end of the engine and is directly linked to, or otherwise engaged via gearing with, a crankshaft of the engine. By contrast, a supplemental apparatus having a high drive load requirement, such as a power steering pump, a compressor for an air conditioner, and/or an alternator, is typically disposed on a side of the engine and near either a front end or a rear end of the engine. This type of supplemental apparatus is also typically driven by a belt or a chain connected with an end of the engine crankshaft.
2. Description of Related Art
As described in, for instance, the specification of West German Patent Publication No. 3,838,073, an engine may be mounted at a backward slant or a tilt so that it leans toward a rear end of a vehicle. The engine of the disclosure of this publication is mounted parallel to a transmission so as to extend transversely of the body of the vehicle, and has a supplemental apparatus disposed in a space located in front of the engine. This space is formed by the backward slant or tilt of the engine. A belt, linked to the engine crankshaft, drives the supplemental apparatus disposed in the space located in front of the engine.
There is a demand to compactly mount the supplemental apparatus in the volume available for the engine. Such a demand is met by using an unused space, which is located at a front or rear side of an oil pan of the engine. In order to locate the supplemental apparatus in the dead or unused space around the oil pan, however, it is necessary to reinforce a supporting portion or bearing of the supplemental apparatus in order to provide it with a sufficient rigidity to resist tension applied by the belt. It is also necessary to provide a space in which to locate a drive shaft, which links the supplemental apparatus with the engine crankshaft. These requirements undesirably force the volume of the oil pan to be reduced; therefore, the volume of oil available to the engine may be insufficient in some cases. Consequently, as is clear from the specification of the West German publication mentioned above, it is difficult to receive the supplemental apparatus in the dead or unused space around the oil pan in the desired manner. Another requirement is that it must be possible to assemble the supplemental apparatus to the engine readily. More particularly, in order to assemble a plurality of supplemental apparatuses and their drive mechanism to the engine in a fully automated assembling line, it is essential to provide the supplemental apparatuses and their drive mechanism as a single unit. However, it is difficult to unite conventional belt-driven supplemental apparatuses and their drive mechanism as a single unit. In addition, for such belt-driven supplemental apparatuses, it is also essential to improve the structural rigidity of a supporting element or supporting elements for the drive shaft, due to the presence of a considerably increased belt tension. Providing such a supporting element or supporting elements, however, results in both an increased engine weight and the occurrence of some vibrations.
Particular problems associated with an oil pump of an engine of the prior art also exist. In a layout of a supplemental apparatus and its drive mechanism according to the prior art, an oil passage or "sub-gallery" between the oil pump and its associated oil filter is required to be relatively long. As a result, a loss of pressure is present in the sub-gallery. This is because the oil pump is generally disposed near a crankshaft and is driven by the crankshaft through gearing. Further, because a limited space is present, it is difficult for an oil filter to be located near both the oil pump and the crankshaft. Disposing the oil pump and its associated oil filter separately from each other results in a long distance between the oil pump and the oil filter and in an increased oil flow resistance, or pressure loss.
The layout of the oil pump cannot be considered alone without also considering the layout of a water pump, which also serves as a supplemental apparatus. Both the oil pump and the water pump provide a low load to drive, as mentioned above, and the oil pump and the water pump can be provided close to each other in a layout. In order to provide a compact supplemental apparatus layout and drive as many of the supplemental apparatuses as possible by a single drive shaft, at least the oil pump and the water pump must be driven by the same drive shaft and disposed inside the oil pan. The number of bearings for these pumps should also be reduced so that no more of these bearings than are necessary are provided. Additionally, the oil pump should be disposed in a location in which an oil leak will never happen. It is important for a compact and satisfactory layout of the supplemental apparatuses to satisfy all these conditions or considerations.
In an arrangement such as that described above, a flywheel of the engine is generally connected to rear end of the crankshaft at which a clutch is coupled. A pulley for driving a supplemental apparatus, through a belt, is generally fixed at a front end of the crankshaft, opposite to the end of the crankshaft which is connected with the clutch. Furthermore, the pulley on the front side of the crankshaft may have a built-in damper mechanism which dissipates twisting vibrations of the crankshaft. Since the pulley on the front end of the crankshaft itself typically has considerable weight, putting the damper in the pulley so as to surround an axis portion, or a portion around the center axis of the pulley, and an outer mass portion, or an outside ring portion, helps damp the crankshaft against twisting vibrations. The damper may, for example, be formed of an elastic member made of rubber. The amplitude of the twisting vibrations is at a maximum on the front end of the crankshaft, while a vibration node is located at the rear end of the crankshaft on which the flywheel is mounted and connected to the transmission via the clutch. Consequently, the twisting vibration of the crankshaft is effectively dissipated by the aid of the pulley on the front end of the crankshaft, which drives the supplemental apparatus.
The provision of such a damper in a pulley mounted on the front end of the crankshaft is effective in dissipating twisting vibrations, but is ineffective for dissipating bending vibrations of the crankshaft. Because the crankshaft bends between the journals, especially at its rear end portion where the flywheel is attached, due to vibrations of the rearmost end cylinder, it causes the flywheel t o vibrate, so that bending of the crankshaft increases noise and is produced. Accordingly, providing the damper on the front end of the crankshaft, located far from the rear end thereof, where bending is the most serious, cannot effectively reduce the bending vibration. In addition, although the damper on the front end of the crankshaft lessens the vibrations of the crankshaft more effectively as it is made heavier, since a natural frequency of the damper is lowered with an increase in weight of the flywheel, the range of vibrations of the crankshaft which can be damped, by an inverted phase, is narrowed. Consequently, the rigidity of the crankshaft against twisting is decreased in the range of the same phases of vibration of the crankshaft as of the flywheel.
Twisting vibration problems typically arise in engines having supplemental apparatuses. If a supplemental apparatus is driven by a chain or a belt linked with a crankshaft, a shift in angular velocity of the crankshaft is transmitted to the supplemental apparatuses through the chain or the belt. Twisting vibration will be transmitted to the supplemental apparatuses, even if a structure is used which provides drive power for the supplemental apparatuses which is supplied from the rear end or minimum point of the twisting vibration so as to eliminate twist vibration influences. As a result, extraordinary gear engagement noise may occur at the connection between the gears.